Method and position sensor assembly for determining a mutual position between a first object and a second object

Abstract

A method and position sensor assembly for determining a mutual position between a first object and a second object. The position sensor assembly includes a first body, a coil, a control unit, and a sensor circuit, the first body being reciprocally displaceable in the axial direction in relation to the coil. The sensor circuit includes in turn a comparator connected to a first branch including the coil, a power switch, and a measuring resistance coupled in series with each other.

The invention claimed is: 
     
       1. A method for determining a mutual position between a first body ( 10 ) and a coil ( 11 ) by means of a position sensor assembly, which comprises said first body ( 10 ), said coil ( 11 ), a control unit, and a sensor circuit ( 12 ), said first body ( 10 ) being reciprocally displaceable in the axial direction in relation to said coil ( 11 ), the sensor circuit ( 12 ) comprising a comparator ( 15 ) connected to a first branch comprising said coil ( 11 ), a power switch ( 16 ), and a measuring resistance ( 18 ) coupled in series with each other, the comparator ( 15 ) being arranged to obtain and compare an instantaneous measuring voltage across the measuring resistance ( 18 ) and an instantaneous reference voltage, and being arranged to, based on the mutual relationship between the measuring voltage and reference voltage, generate a state change of a digital output signal, the method comprising the steps of:
 sending a rising edge of a digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from open to closed, 
 in the control unit, detecting a first state change of the output signal from the comparator ( 15 ), and 
 determining a mutual position between said first body ( 10 ) and said coil ( 11 ) based on the time delay between the rising edge of the input signal pulse and the first state change of the output signal, 
 or comprising the steps of: 
 sending a rising edge of a digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from open to closed, 
 in the control unit, detecting a first state change of the output signal from the comparator ( 15 ), 
 in the control unit, detecting a second state change of said output signal, and 
 determining a mutual position between said first body ( 10 ) and said coil ( 11 ) based on the time delay between the first state change of the output signal and the second state change of the output signal. 
 
     
     
       2. The method according to  claim 1 , wherein said first state change of the output signal from the comparator ( 15 ) is a rising edge of a digital output signal pulse, and wherein said second state change of the output signal from the comparator ( 15 ) is a falling edge of said digital output signal pulse. 
     
     
       3. The method according to  claim 1 , wherein the method, in addition to the steps of:
 sending a rising edge of a digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from open to closed, 
 in the control unit, detecting a first state change of the output signal from the comparator ( 15 ), and 
 determining a mutual position between said first body ( 10 ) and said coil ( 11 ) based on the time delay between the rising edge of the input signal pulse and the first state change of the output signal, 
 also comprises the step of: 
 based on the detection of said first state change of the output signal from the comparator ( 15 ), sending a falling edge of said digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from closed to open. 
 
     
     
       4. The method according to  claim 1 , wherein the method, in addition to the steps of:
 sending a rising edge of a digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from open to closed, 
 in the control unit, detecting a first state change of the output signal from the comparator ( 15 ), 
 in the control unit, detecting a second state change of said output signal, and 
 determining a mutual position between said first body ( 10 ) and said coil ( 11 ) based on the time delay between the first state change of the output signal and the second state change of the output signal, 
 also comprises the step of: 
 based on the detection of said second state change of the output signal from the comparator ( 15 ), sending a falling edge of said digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from closed to open. 
 
     
     
       5. A position sensor assembly for determining a mutual position between a first object ( 1 ) and a second object ( 2 ), which position sensor assembly comprises:
 a first body ( 10 ) connectable to said first object ( 1 ), a coil ( 11 ) connectable to said second object ( 2 ), a control unit, and a sensor circuit ( 12 ), said first body ( 10 ) being reciprocally displaceable in the axial direction in relation to said coil ( 11 ), 
 the sensor circuit ( 12 ) comprises: 
 a first branch comprising said coil ( 11 ), a power switch ( 16 ) having an input operatively connected to said control unit for receiving individual digital input signal pulses, and a measuring resistance ( 18 ), the coil ( 11 ), the power switch ( 16 ), and the measuring resistance ( 18 ) being coupled in series with each other, 
 a comparator ( 15 ), which is connected to said first branch via a first input ( 20 ) to obtain an instantaneous measuring voltage across the measuring resistance ( 18 ), and which further comprises a second input ( 21 ) for obtaining an instantaneous reference voltage, and an output ( 22 ) operatively connected to said control unit for outputting individual state changes of a digital output signal based on the mutual relationship between said measuring voltage and said reference voltage. 
 
     
     
       6. The position sensor assembly according to  claim 5 , wherein the sensor circuit ( 12 ) comprises a feedback branch ( 25 ) connected between the output ( 22 ) of the comparator ( 15 ) and the second input ( 21 ) of the comparator ( 15 ). 
     
     
       7. The position sensor assembly according to  claim 5 , wherein the first branch of the sensor circuit ( 12 ) is connected between a voltage source ( 19 ) and ground, and wherein the sensor circuit ( 12 ) comprises a second branch, which is connected between the voltage source ( 19 ) and ground, and which comprises a first reference resistance ( 23 ) and a second reference resistance ( 24 ), which are coupled in series with each other, the second input ( 21 ) of the comparator ( 15 ) being connected to said second branch at a point situated between said first reference resistance ( 23 ) and said second reference resistance ( 24 ). 
     
     
       8. The position sensor assembly according to  claim 7 , wherein the power switch ( 16 ) is disposed adjacent to ground. 
     
     
       9. The position sensor assembly according to  claim 8 , wherein the sensor circuit ( 12 ) comprises a synchronization resistance ( 26 ) that is connected in parallel across the power switch ( 16 ), each of the first branch and the second branch of the sensor circuit ( 12 ) being coupled in series with the synchronization resistance ( 26 ) as well as the power switch ( 16 ). 
     
     
       10. The position sensor assembly according to  claim 5 , wherein said first body ( 10 ) is an electrically conductive body, preferably manufactured from aluminum. 
     
     
       11. The position sensor assembly according to  claim 5 , wherein said first body ( 10 ) is displaceable in the axial direction internally of the coil ( 11 ). 
     
     
       12. The method according to  claim 2 , wherein the method, in addition to the steps of:
 sending a rising edge of a digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from open to closed, 
 in the control unit, detecting a first state change of the output signal from the comparator ( 15 ), 
 in the control unit, detecting a second state change of said output signal, and 
 determining a mutual position between said first body ( 10 ) and said coil ( 11 ) based on the time delay between the first state change of the output signal and the second state change of the output signal, 
 also comprises the step of: 
 based on the detection of said second state change of the output signal from the comparator ( 15 ), sending a falling edge of said digital input signal pulse from the control unit to the power switch ( 16 ) to produce a state change of the power switch ( 16 ) from closed to open. 
 
     
     
       13. The position sensor assembly according to  claim 6 , wherein the first branch of the sensor circuit ( 12 ) is connected between a voltage source ( 19 ) and ground, and wherein the sensor circuit ( 12 ) comprises a second branch, which is connected between the voltage source ( 19 ) and ground, and which comprises a first reference resistance ( 23 ) and a second reference resistance ( 24 ), which are coupled in series with each other, the second input ( 21 ) of the comparator ( 15 ) being connected to said second branch at a point situated between said first reference resistance ( 23 ) and said second reference resistance ( 24 ).